Ineed a little bit of halp ! a bag of pennies weighs 5.1 kilograms. each penny weighs 2.5 grams. about how many pennies are in the bag?

Hello!

so we have a total weight of 5.1kg and we are told that each penny weighs 2.5g.

so we need to convert either one to the same units first. we know there are 1000g in 1kg so 2.5g=0.0025kg now we have both in the units of kg, so we can just take 5.1kg/0.0025kg=2040 pennies in the bag. 

we can check ourselves here by taking 2040 * 2.5g and we get 5100grams which equals 5.1kg  

hope this helps. any questions please just ask. thank you kindly